Method of and apparatus for treating wells



i @UI @wenn @www Oct. 24, 1944. J. J. GRE-:BE 2,361,195

METHOI? 0F AND APPARATUS FOR TREATING WELLS Filed Aug. z8', 1940 ,vv-Ww l ATTORNEYS Patented Oct. 24, 1944 @iijii ilUUm METHOD OF AND APPARATUS FOR TREATING WELLS John J. Grebe, Midland, Mich., assig'nor to The Dow Chemical Company, Midland, Mich., a

corporation of Michigan Application August 28, 1940, Serial No. 354,506

('Cl. 16S-2) 4 Claims.

particularly concerns a method whereby a fluid treating agent may be simultaneously introduced into at least two zones in such a manner that for any selected rate of flow of uid agent being directed to one zone, a definite fixed rate of flow is also directed to the other zone.

The bore of a well oftentimes penetrates more than one stratum or zone of a productive nature and it is usually desirable when treating such wells with a fluid treating agent to be assured that some of the fluid will be injected into each productive zone. In some instances it is even desirable to be assured that for any given rate of flow of fluid treating agent being directed to one zone, a proportional rate of iiow will also be directed into the other zone or zones, as the 25 For example, in the tre,atment.-..

case may be.

,Wlthaidai alwellpenctrating...more than one productive stratum in calcareous earth or rock to bring about an increase in production, it is usually desirable that a method of treatment be provided to positively ensure that one stratum or zone will receive acid at a definite rate relative to the other stratum, for otherwise all of the acid may drain into the zone having the most porous structure, with the result that little or no increase in production will be obtained from the zone into which the acid does not penetrate readily. It is further desirable when treating wells of such nature that the introduction of the fluid agent into each stratum takes place at the same time in order to avoid the necessity of carrying out a separate treatment of each stratum or productive zone.

The term zones used herein and in the appended claims is intended to refer not only to separately defined strata but to different sections or portions of one producing formation or stratum.

It is, therefore, the principal object of the preselected rates of flow regardless of the ease with which the fluid treating agent iiows into one of the productive Zones.

Another object of the invention is to provide a method whereby the rate of ow of fluid treating agent being directed to one zone acts to direct a proportional rate of flow of fluid treating agent to another zone.

Still another object of the invention is to provide a method and apparatus whereby a fluid treating agent may be simultaneously introduced into at least two strata or zones while the fluid in the well bore about to enter one Zone is maintained out of contact with the fluid about to enter the other zone or zones.

Still further objects and advantages will be apparent as the description of the invention proceeds.

The invention then resides in the method and apparatus hereinafter more fully described and particularly pointed out in the claims, the accompanying drawing and following description setting forth in detail a mode of carrying out the invention, such mode illustrating, however, but one of the various ways in which the invention may be put into operation.

. 4In the accompanying drawing,

Fig. 1 is a fragmentary sectional view of a well bore in vertical cross section showing an embodiment of the invention.

Fig. 2 is a sectional view taken along line 2-2 of Fig, l, looking in the direction of the arrows, showing a detail of construction of a portion of the apparatus.

Fig. 3 is a fragmentary sectional view of Fig. 1 showing that section of the apparatus below the packing element III which includes the discharge port I9 and illustrates additional elements associated with the discharge port which act to modify the action of the apparatus.

As shown in Fig. l. the upper portion I of the well bore is cased with metal pipe 2 down to a point 3 where it is cemented in place by cement 4. The lower portion of the wel] bore 5 penetrates a productive stratum 6, and impervious stratum 1, and ends in a second productive stratum 8. Conduit 9, attached to a conventional well tubing string (not shown) extends into the well and is connected at its lower end to packer I0, as by means of rivets II. Conduit 9 is provided with a slotted opening I2 at a point adjacent the upper productive stratum 6, and also with lug members I3 located on the interior surface thereof at a point near the lower end. A tubu- 12111. member I4 is disposed interiorly of the conduit 9, and is provided with an enlarged upper end I5 which engages the conduit 9 in sliding sealing relation. The tubular member I4 is provided with a port I6 which is adapted to communicate or register with the slotted opening I2 in conduit 9. The tubular member I4 is also provided on its outer surface with an annular metal ring I1, which forms a seal between conduit 9 and tubular member I4, and also serves to engage lug members I3 of the conduit 9 so as to limit the travel of the conduitI 9 over the tubular member I4. Tubular member I4 extends downwardly through the packing element ID and is attached to the lower end of packer I0 or by rivets (not shown). The lower end of the tubular member I4 is shown in threaded engagement with a cap I8, which rests upon the bottom of the well bore. Tubular member I4 is provided at a point near its lower end with a port I9. This port I9 communicates with the well bore adjacent the lower productive formation 8 at a point below the packing element I0. Disposed within the tubular member I4, a second tubular element is secured at either end to the wall of the tubular member I4 by means of annular metal rings 2| and 22. The upper ring 2| is provided with ports 24 through which fluid may flow from conduit 9 into the annular space between tubular elements I4 and 20. Element 20 is provided with slotted ports 25 centrally located therein through which the fluid may pass into the interior of tubular element 20. A metal ring 23 acts to seal the annular space between the tubular elements I4 and 29 at a point intermediate the ends of element 20 and below the slotted ports 25. The upper end of the tubular element 2U is shown covered with a cap 26 having an opening therein which is in communication with port I6 through conduit 21. The lower end of element 20 opens into the tubular element I4 which in turn communicates with the well bore through port I9. Within the tubular element 20, two pump units designated generally by numeral 28 are shown disposed in such a manner that one is caused to drive the other. The pump units consist of driving worm gears 29 intermeshed with driven mating gears 3U. The shafts of worm gears 29 and 30 are provided at the eX- treme upper and lower ends with thrust bearings 3|. Ports 32 extend through the bearings 3| and serve as channels through which fluid may discharge from the pumps. The ported bearings 3| are shown secured to the wall of tubular member 20 in conventional manner as by means of screws 33. 'Ihe driving Worm gears 29 of each pump unit are coupled to each other by coupling 34, so that as one driving gear is caused to turn, the other must also turn. Bearing members 35, secured to the wall of element 20 by screws 36, are located at points above and below the coupling 34 and support the shafts of worm gears 29 and mating gears 30. Ports 31 extend through bearing members 35 and serve as ow channels for the fluid entering the pump units. The gear members of pump units 28 are surrounded by a housing 38, more particularly shown in Fig. 2, which acts as a seal around the gear members and prevents fluid flow when the intermeshed worm gears 29 and 30 are not in rotating movement.

In the fragmentary sectional view shown in Fig. 3 the lower discharge port I9 is shown equipped with a back pressure valve. The housing 39 of the valve is shown attached to tubular member I4 by means of weld 40. The valve assembly consists of a ported housing 39 having a well 4| in which valve stem 42 slides as pressure applied interiorly of the tubular member I4 overcomes the pressure of spring 43 acting to force the valve into seated position against discharge port I9.

The operation of the method will be best understood from the following description wherein the aparatus is employed to carry out the simultaneous introduction of an acid solution into two productive strata separated by an impervious stratum. Conduit 9 connected to the well tubing (not shown) is run into the well and packing element I0 seated against the impervious stratum 1, as by applying weight on conduit 9 causing it to slide over tubular element I4. Thereafter the acid is introduced into the well through the well tubing where it ows downwardly into conduit 9 and through ports 24 in the ring 2|, and thereafter through the slotted ports 25 in tubular element 20. As pressure is applied to the acid, it flows through the ports 31 in bearings 35 and causes the intermeshed worm gears 29 and mating gears 30 to turn. As the pressure being applied to the acid causes the intermeshed worm gears to turn, a definite xed quantity of acid is carried through each pump unit for every complete revolution of the gear shafts in the manner common to conventional gear pumps. The fluid escaping from the lower pump unit passes through the lower ported bearing 3| and out through port I9 into contact with stratum 8 while the uid escaping through the upper pump unit passes through the uper ported ybearing 3| and conduit 21 and comes in contact with the upper productive formation B. If desired, a quantity of oil or the like may be introduced into the annular space between the tubing 9 and the well casing 2 to control the level to which the acid can rise in the well bore as it is being displaced into stratum 6. As the introduction of acid and application of pressure co-ntinues, the acid is forced out into each formation and the rate of flow to each stratum depends entirely upon the capacity of the pump unit communieating with each stratum. Since the one pump unit acts to drive the other, and neither can turn without the other also turning, each stratum receives acid at a rate proportional to the capacities of the pump units being employed. After the desired amount of acid has been introduced into the productive strata and allowed time to react, the packing element may be unseated and the assembly withdrawn from the well. The spent or partially spent acid reagent may then be withdrawn, as by bailing, and the well put back into production.

The modification illustrated in Fig. 3 may be employed in conjunction with either discharge port if desired. The spring loaded back pressure valve may be advantageously used to correct for differences in formation pressures between the two zones so that the device can be operated at more nearly comparable pressure drops across each pump.

It is to be understood that several pump units maybe placed on a common driving shaft so that several formations or zones may be separately and simultaneously treated. In such cases fluid may be fed to all the pumps from a common source while the discharge from the various pumps is separately conveyed to each zone.

In the foregoing manner, two or more strata in a well bore may be simultaneously and independently treated with a fluid reagent, while assurance is had that each formation will receive a predetermined quantity of the fluid treating agent.

The method will be found to have most general use in connection with an acidtreatment wherein a solution of hydrochloric or other acid is introduced into the formation to bring about solution of the earth or rock formation and thus an increase in size of the flow channels through which the desired mineral fluid flows to the well. In such treatments it will usually be found preferable to employ an aqueous solution of hydrochloric acid of from to 25 per cent concentration. If desired, such an acid may be inhibited against corrosive attack upon iron or steel in the manner taught in U. S. Patent No. 1,877,504.

Although the method has been described with particular reference to an acid treatment, it is to be understood that any fluid treating agent may be introduced in accordance with the method of the invention. Examples of such treating agents are paraflln solvents, liquid sealing agents, and the like.

I claim:

l. In a method of introducing a fluid agent into at least two zones penetrated by the bore of a well, the steps which comprise introducing the fluid agent into the well through a single conduit means and simultaneously directing it to each zone at a substantially fixed ratio of rates of flow.

2. In a method of introducing a iluid agent into at least two zones penetrated by the bore of a well, the steps which comprise simultaneously introducing the fluid agent into each zone through a single conduit means having openings therein adapted to communicate with each zone, separating the zones from each other by sealing off the annular space between the conduit and the well bore at a point between said zones, and employing the rate of flow of fluid to one zone to control the rate of flow of fluid agent to the other zone.

3. In a well treating device for the simultaneous injection of a fluid agent into at least two zones penetrated by the bore of a well: conduit means adapted to be disposed in a well bore, said conduit having openings therein adapted to communicate with each zone; sealing means surrounding the conduit adapted to seal the an- Minimi www nulus in the well bore around the conduit at a point between said zones; geared fluid displacement units each adapted to operate either as a fluid motor or pump disposed in said conduit and each having a fluid inlet and outlet, respectively, the fluid inlets being in communication with the interior of said conduit; a fluid connection from the outlet of one of said units to one of the openings in the conduit; a fluid connection from the outlet of the other of said units to the other opening in the conduit; and means linking together the fluid displacing elements of the said units so that the passage of fluid into the well bore from the conduit through one of the said units actuates it as a motor driving the other as a pump, the fluid passing through the pump into the well bore thereby being in xed proportion to the iiuid passing through the unit acting as a motor.

4. In a well treating device for the simultaneous injection of a fluid agent into at least two zones penetrated by the bore of a well: conduit means adapted to be disposed in a well bore, said conduit having openings therein adapted to communicate with each zone; sealing means surrounding the conduit adapted to seal the annulus in the well bore around the conduit at a point between said Zones; geared fluid displacement units each adapted to operate either as a fluid motor or pump disposed in said conduit and each having a fluid inlet and outlet, respectively, the fluid inlets being in communication with the interior of said conduit; a fluid connection from the outlet of one of said units to one of the openings in the conduit; a fluid connection from the outlet of the other of said units t0 the other opening in the conduit; means linking together the fluid displacing elements of the said units so that the passage of fluid into the well bore from the conduit through one of the said units actuates it as a motor driving the other as a pump, the fluid passing through the pump into the well bore thereby being in fixed proportion to the fluid passing through the unit acting as as motor; and a back pressure valve co-operable with one of the openings in the conduit adapted to open upon application of pressure from 'the interior of the conduit.

JOHN J. GREBE. 

